A typical solar cell includes a heterojunction formed between two silicon layers, a p-doped base and an n-doped emitter layer. An antireflection coating is generally present on top of the emitter layer, so as to enhance trapping of incident light by preventing the light from begin reflected off of the surface of the solar cell.
Multi-crystalline silicon is often used to form the base and emitter layer. In such multi-crystalline silicon solar cells, it is desirable to achieve good light trapping properties by processing the surface of the multi-crystalline silicon such that when the antireflection coating is deposited thereon (the antireflection coating is a conformal layer) a roughened, and thus enhanced light trapping, surface results.
Due to the fact that the surface of multi-crystalline silicon is isotropic in front of acid or alkaline, wet etch without patterning could not create required surface roughness to provide good light trapping property. Patterning and reactive ion etching (RIE) processes can be used, in theory, to achieve the above goal. However, from a practical standpoint, the costs associated with the RIE approach are prohibitively high.
Therefore, effective, low-cost solutions for multi-crystalline silicon processing to achieve the above-described results, would be desirable.